This is a broad program investigating the molcular structure of the genome of tranforming viruses and basic mchanism in gene expression and gene recombination. Specific programs include analysis of the nature and mode of action of interferon, the reconstruction of DNA recombining systems in vitro, the mechanism of replication of small DNA viruses, the elucidation of the complete sequence of SV40 DNA, the characterization of SV 40 gene products in transformed cells and the biologic properties of strains of EB virus.